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Discussion Starter · #1 ·
'03 Forester, 165K miles.

This morning I had a catastrophic failure of my radiator. I'm getting the radiator replaced and I want to know what else I should fix at the same time. I've had several symptoms pop up this past week and I can't sort out if it's related or not. In order of appearance:

Past week and a half
- Ignition making funny noise when starting.

- Wet spot on ground under radiator. (cooling system leaking obviously)
- AC was noticeably weak.

This Morning
- After 20-minute drive, tried to turn on engine and BARELY able to do so.
- 30 seconds after starting, notice temperature was high, steam billowing out under the hood and coolant was sprayed over much of the engine.
- Setting the heater to full blast did nothing but pump out cool/tepid air.
- I couldn't see if coolant was low or gone, but topped reservoir off with water as a stop-gap. Despite this, the engine temp still ran hot and heater air was still tepid. As I limped to the mechanic (< 1 mile away) the engine even shut off and I had to wait several minutes before I could drive again.

SO, are there other parts that are likely failed? Thermostat and water pump (replaced 5 yrs ago at 110K)? Heater core? Starter? (Batter and alternator recently replaced.)

2017 Forester XT Touring CVT
247 Posts
Wash down the engine bay really well to keep that left over coolant that sprayed all over the place from eating at the metal and paint.

1) get a subaru OE genuine radiator. i learned my lesson and purchased two OE fit but not genuine subaru radiators and chased leaks and problems and eventually has en over heat. later i bought the subaru genuine one and everything was great until the head gasket leak slowly got worse and let loose.

2)do a head gasket leak test using a garbage radiator that wont leak. make sure all the air is purged out of the system first. make sure you did not do any damage. once those engines overheat in my experience they kill the head gasket. others have been very lucky, or should i say i have bad luck.

3) if everything passed do a total cooling system flush using only distilled water. not flush chemicals or additives

4) replace thermostat and radiator cap, use a subaru genuine one. replace rubber hoses now if they appear cracked or hard. also replace hose clamps

5) refill with coolant and water mix, i think your car still uses green ethyl glycol. check with the parts guys at your subaru dealer for the specs.

6) if it take the green stuff then go and find the green stuff. do not get the mix with any other coolant kind. it takes green get green. if it takes blue get blue from the parts counter at the dealer. you only need two gallons of premixed.

7) make sure when your filling that you purge all the air out of the system. i have seen some guys use ramps to get the front of the car where the radiator cap is up to make it the highest point.

that reservoir does not put coolant in the system if the engine is hot and the coolant system is pressurized.
next time you encounter an overheat condition pull over let the car totally cool down that means waiting for an hour or more. call a tow is the best way to prevent any further damage.

the reservoir acts more like an expansion tank. as the engine and coolant heats up. the coolant becomes pressurized. the radiator cap acts as an air purge and relief valve. sending coolant pushed out of the radiator to he expansion tank.

when you shut the car off, the engine and coolant cools. there is a point when the system cools enough to begin drawing a vacuum. the vacuum then pulls the expelled and captured coolant back in to the cooling system. we do not want air in the system as it causes corrosion and fluid trapping which leads to no coolant flow through an areas of the system.

its important to check the coolant level in the expansion tank if the level drops too low the vacuum effect will suck air in to the system.
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